The present invention relates to an intracranial pressure relief valve and, more particularly, to a valve for shunting excess cerebrospinal fluid (CSF) from a ventricle in the brain to another location in the body of a patient when the epidural pressure reaches a predetermined magnitude.
Hydrocephalus is a condition in which the body, for any one of a variety of reasons, is unable to relieve itself of CSF which collects in the ventricles of the brain. The excessive collection of CSF in the ventricular spaces results in an increase of both epidural and intradural pressures. This in turn causes a number of adverse physiological effects including compression of brain tissue, impairment of blood flow in the brain tissue and impairment of the brain's normal metabolism.
Treatment of a hydrocephalic condition frequently involves relieving the abnormally high intracranial pressure. Accordingly, a variety of CSF pressure regulator valves and methods of controlling CSF pressure have been developed which include various forms of check valves, servo valves or combinations thereof. Generally, such valves serve to divert CSF from the ventricles of the brain through a discharge line to some suitable drainage area of the body, such as the venous system or the peritoneal cavity. Check valves operate by opening when CSF pressure exceeds pressure in the discharge line by a predetermined value.
Servo valves for use in the treatment of hydrocephalus typically allow drainage of CSF as needed to maintain a desired intracranial pressure as measured within the epidural or intradural spaces. A sensor responsive to pressure in such a space, establishes a pressure threshold which, when exceeded by the pressure in the epidural or intradural space results in opening of the valve to allow drainage of excess CSF. Preferably, the threshold so established is independent of ventricular CSF pressure.
For optimum performance, it is desirable that a servo valve have a high sensitivity to sensed pressure so that the desired intracranial pressure can be maintained with a high degree of accuracy. The present invention is directed to a servo valve which is extremely responsive to minute changes in the pressure of the fluids, thereby providing very accurate control of intracranial pressure. In this valve, the body fluids act on both sides of a movable area or diaphragm of relatively substantial surface area so that the valve is responsive to relatively small pressure differentials. Fluid in pressure communication with the discharge area of the body is applied to one side of the diaphragm while fluid in pressure communication with a sensor implanted in the epidural or intradural space is applied to the opposite side of the diaphragm. Relative movement of the diaphragm results in actuation of a valve assembly thereby controlling passage of CSF from the ventricular spaces to the selected discharge area within the body. As displacement of the diaphragm depends primarily on the difference between the sensor and discharge line pressures, a regulator valve having a threshold largely independent of ventricular CSF pressure is provided.
In view of the foregoing, it is a general object of the present invention to provide a new and improved pressure regulator valve for relieving intracranial pressure caused by the presence of excess CSF in the ventricles of the brain.
It is a more specific object of the present invention to provide a CSF pressure regulator valve which maintains a desired predetermined intracranial pressure.
It is still a more specific object of the present invention to provide a CSF pressure regulator valve which maintains a desired intracranial pressure independent of ventricular CSF pressure.